The present invention relates to an improved valve gear train for an internal combustion engine, and more particularly, to an improved and simplified lubrication arrangement for the valve gear train.
In certain types of internal combustion engines, each of the rocker arms, which control the opening and closing movement of the engine poppet valves, is pivoted by means of a push rod. The upper end of the push rod is in engagement with the rocker arm, while the opposite (lower) end of the push rod is in engagement with a cam follower assembly, which receives a cyclical input motion by its engagement with a cam profile on the engine cam shaft. Typically, the cam follower is a roller member and the assembly includes a hydraulic lash compensation element.
Thus, the present invention is directed primarily to internal combustion engines known generically as being of the push rod type. More particularly, the invention relates to an engine valve gear train in which the push rod is specifically a hollow push tube, rather than a solid rod. In some engine designs, a hollow push tube is used to transmit the cyclical motion of the cam lobe into corresponding motion of the rocker arm, so that the hollow push tube can comprise part of the engine lubricant circuit.
The type of valve gear train described above has been in widespread commercial use throughout the world, has become increasingly popular, and has performed in a generally satisfactory manner. However, in such valve gear train using hollow push tubes, it has typically been necessary to gun drill both the engine block and the rocker arm shaft to provide the necessary lubricant passages. The gun drilled passage in the engine block would intersect the bore in which the cam follower assembly is disposed, thereby providing oil to the hydraulic lash compensation element of the follower assembly.
The gun drilled passage in the rocker arm shaft would be primarily for the purpose of lubricating the rocker arm, and its various interfaces with other valve gear train components, such as the poppet valve and the push tube. As is well know to those skilled in the art of engine manufacturing, gun drilling adds substantially to the cost and complexity of machining the cylinder block and the rocker arm shaft, thus adding substantially to the overall manufacturing cost of the engine.
Accordingly, it is an object of the present invention to provide an improved lubrication arrangement for an internal combustion engine of the type having a push tube valve gear train, which overcomes the above-described problems of the prior art lubrication arrangement.
It is a more specific object of the present invention to provide such an improved lubrication arrangement for a push tube type valve gear train which eliminates the necessity of gun drilling lubricant passages in the engine block and the rocker arm shaft.
It is a further object of the present invention to provide an improved lubrication arrangement which achieves the above-stated objects, and in which lubricant is communicated to the interior of the push tube primarily by splash oil within the cylinder head.
The above and other objects of the invention are accomplished by the provision of an improved lubrication arrangement for an internal combustion engine of the type including an engine block defining a combustion chamber and a cam shaft rotatably supported relative to the engine block for providing cyclical input motion. A cylinder head is in operable engagement with the engine block and includes poppet valve means for controlling the flow to and from the combustion chamber. A rocker arm is pivotable about a fixed fulcrum location and includes a valve contacting portion in engagement with the poppet valve means for transmitting the cyclical input motion thereto. The engine includes a source of pressurized fluid and the cylinder head defines a main fluid passage in fluid communication with the source. A cam follower, including a hydraulic lash compensation device, is operably associated with the cam shaft, and a push tube is disposed in series between the cam follower and the rocker arm and is operable to transmit the cyclical input motion from the cam shaft to the rocker arm.
The improved lubrication system is characterized by a carrier structure fixed relative to an upper surface of the cylinder head and including the fixed fulcrum location. The carrier structure defines a lubrication passage providing fluid communication of lubrication fluid from the main fluid passage to the fixed fulcrum location. The engine block and the cylinder head cooperate to define a fluid chamber surrounding the push tube, whereby the lubrication fluid flows out adjacent the fixed fulcrum location and flows under the influence of gravity into the fluid chamber. The push tube defines a plurality of openings whereby the lubrication fluid flows from the fluid chamber into the interior of the push tube. The push tube and the lash compensation device cooperate to define fluid passage means permitting lubrication fluid to flow from the interior of the push tube into a reservoir defined by the lash compensation device.